Maple or birch water evaporator system

ABSTRACT

A system for producing maple syrup or birch syrup from maple or birch water, comprising an evaporating pan under controlled pressure, a condenser immersed in maple or birch water in the evaporating pan, and a compressor, pressurizing vapor generated by evaporation of maple or birch water in the evaporating pan, the condenser directing the pressurized vapor provided by the compressor to the maple or birch water within the evaporating pan, thereby further evaporating the maple or birch water and further generating vapor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/435,973 filed on Mar. 30, 2012, which itself claims benefitof U.S. provisional application Ser. No. 61/470,581, filed on Apr. 1,2011. All documents above are incorporated herein in their entirety byreference.

FIELD OF THE INVENTION

The present invention relates to a maple or birch water evaporatorsystem.

BACKGROUND OF THE INVENTION

Typically, maple water is transformed into maple syrup in an evaporator,standardly fired by wood, oil or gas. The water is heated until itboils. From the time the maple water is poured into the evaporator tothe time it turns into syrup, it undergoes a complex chain of chemicalreactions which produce the characteristically maple color and flavor.Typically, around 40 liters of maple water are evaporated to produce 1liter of syrup. Most of the water in the maple water evaporates duringthis process, leaving concentrated maple syrup. Maple water has a sugarcontent comprised between about 1 and 4 Brix, while maple syrup has asugar content of about 66 Brix.

Generally, the evaporator consists of one or more pans that are placedover a firebox referred to as an arch. The pans are divided intosections to separate the more concentrated maple water from the moredilute. The sections are not closed, so that the maple water can movefreely as the water evaporates therefrom. A flat bottomed pan isreferred to as the syrup pan or finishing pan. Syrup reaches its finalconcentration in this pan. Flues in the bottom of the sap pan greatlyincrease the surface area for heating. Hot gasses from the fire passbetween the flues. The flue pan is positioned toward the back of thefirebox. The maple water enters the flue pan. The syrup pan is placedover the front of the firebox above grates in a wood fired arch as wesee below. The syrup pan and flue pan are connected so that the flow iscontinuous. The maple water in the pans is about 2 inches deep duringactive boiling. The amount of steam that rises is substantial.

The evaporation process is highly energy consuming, energy beingdissipated mainly as water vapor.

There is a need in the art for a maple water evaporator system.

SUMMARY OF THE INVENTION

More specifically, in accordance with the present invention, there isprovided a system for producing maple syrup or birch syrup from maple orbirch water, comprising an evaporating pan under controlled pressure; acondenser immersed in maple or birch water in the evaporating pan; and acompressor pressurizing vapor generated by evaporation of maple or birchwater in the evaporating pan; wherein the condenser directs thepressurized vapor provided by the compressor to the maple or birch waterwithin the evaporating pan, thereby further evaporating the maple orbirch water and further generating vapor.

Other objects, advantages and features of the present invention willbecome more apparent upon reading of the following non-restrictivedescription of specific embodiments thereof, given by way of exampleonly with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the appended drawings:

FIG. 1 is a flowchart of a method according to an embodiment of anaspect of the present invention;

FIG. 2 is a schematical view of a system according to an embodiment ofan aspect of the present invention;

FIG. 3 is a perspective top view of a system according to an embodimentof an aspect of the present invention, with the cover on top of theevaporating pan;

FIG. 4 is a perspective top view of the system of FIG. 3, with the coverremoved from the evaporating pan;

FIG. 5 is a top perspective view of a condenser of a system according toan embodiment of an aspect of the present invention;

FIGS. 6 show a comparison of energy used per volume of maple syrupproduced as a function of the Brix of the maple water entering thesystem, with a system according to the present invention and with astandard oil evaporator as known in the art : A) table of results; B)graph;

FIG. 7 shows a table presenting simulated cost gains for a sugar bushcomprising 10 000 notches, using an evaporator according to the presentinvention and using a standard oil evaporator; and

FIG. 8 schematically shows the use of vapor generated by evaporation ofwater in the maple water, according to an embodiment of the presentinvention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 1 is a flowchart of a method according to an embodiment of anaspect of the present invention. The method generally comprisespressurizing the vapor generated by evaporation of maple water (step120), and directing the energy of this pressurized vapor to the maplewater to an evaporating pan (step 130) for evaporating the water in themaple water present in the evaporating pan, retrieving the vaporgenerated by evaporation of the water in the maple water present in theevaporating pan and pressurizing this retrieved vapor (step 120), whilerecuperating a condensate and heat, for production of maple syrup, in aservo-controlled way.

Once the steady state is reached, the main source of energy forevaporation of the maple water is the pressurized vapor, produced by acompressor from the vapor generated by evaporation of the maple water.

An initial heating stage to first get vapor from the maple water may beachieved using an auxiliary heating unit for heating the maple waterinitially present in the evaporating pan, such as electrical elements ora heat source such as electricity, wood, oil, etc. for example, whichtypically generate low pressure vapor. In the latter case, the vaporthus first generated is then introduced directly in a condenser to startthe process.

As schematically illustrated in FIG. 2, an evaporator system accordingto an embodiment of an aspect of the invention generally comprises anevaporating pan 3, a compressor 8 and a condenser 10.

Initially, the evaporating pan 3 is filled with maple water up to apredetermined level selected such that the condenser tubings areimmerged under the maple water.

Evaporation is first initiated by providing heat to the maple waterpresent in the evaporating pan 3, by using an auxiliary heating unit 5.The auxiliary heating unit 5 is used to rise the temperature of themaple water in the evaporating pan 3 until the pressure in theevaporating pan 3 reaches a predetermined set point, typically between 1and 5 cm of water above atmospheric pressure. Thus, the auxiliaryheating unit 5 first brings the maple water to its boiling temperatureso as to first generate vapor needed to start the compressor 8.

The compressor 8 is then started, fed with the vapor thus generated, formechanically compressing the saturated vapor (D) generated in theevaporating pan 3 into a superheated water vapor (F). As the vapor flowincreases in the compressor 8, the pressure in the evaporating pan 3continues to increase, until it exceeds the predetermined set point,typically between 1 and 5 cm of water above atmospheric pressure asmentioned hereinabove. The heating capacity of the auxiliary heatingunit 5 may then be progressively reduced and finally completely stopped.The system is then able to operate on its own, as will now be described.

Once the compressor 8 is started, evaporation of water in the maplewater in the evaporating pan 3 is achieved by circulating pressurizedvapor, provided by the compressor 8, through manifolds 10 a and tubing10 b of the condenser 10, immersed in the evaporating pan 3.

The pressures, both in the evaporating pan 3 and in the condenser 10,are continuously monitored, by pressure controllers such as sensors forexample. An adjustable pressure regulating valve 11 is used to controlthe pressure within the evaporating pan 3 by varying the heat transferrate delivered by the condenser 10. If the pressure in the evaporatingpan 3 reaches a predetermined set point, typically a pressure between 5and 15 cm of water above atmospheric pressure, the evaporation rate ofthe system is reduced by lowering the pressure in the condenser 10. Onthe opposite, if the pressure in the evaporating pan 3 falls below apredetermined set point, typically a pressure between 1 and 8 cm ofwater above atmospheric pressure, the evaporation rate of the system isincreased by increasing the pressure in the condenser 10. Moreover, anover pressure protection 6 and an under pressure protection 7 areprovided for the evaporating pan 3, as well as a safety valve 9 at theoutput of the compressor 8. Different servo-controlled mechanisms may beused to control the pressure in the evaporating pan 3.

Water may be introduced by a nozzle (E) for example (see FIG. 2) justbefore the inlet of the compressor 8, to reduce vapor superheat beforethe vapor enters the compressor 8. Since the heat transfer rate ishigher when a phase change occurs, water injected by the nozzle (E), inamounts between about 2 and 5% of the main mass flow rate of vapor forexample, providing that the vapor at the output of the compressor 8 ispractically saturated allows the condensing process to start earlier inthe condenser 10, thus maximizing its efficiency.

The surface, the size and the geometry of the condenser 10 are selectedto optimize condensation and energy consumption, as will be describedhereinbelow.

The difference of temperature between the maple water within theevaporating pan 3 and the surface of the manifolds and tubing of thecondenser 10, heated by the compressed vapor circulating through thecondenser 10, is monitored, using temperature controllers. Assessing thetemperature of the compressed vapor circulating through the condenser 10by assuming a certain temperature drop through the tubing walls, it ispossible to determine the pressure of this compressed vapor circulatingthrough the condenser 10, and thus the required compression ratio of thecompressor 8.

The flow of maple water that has to be processed by the system is alsomonitored, by flow controllers. Knowing the rate of water that has to beevaporated from the maple water to be processed, a mass balance allowsdetermining the flow of vapor that is produced by the boiling maplewater. This maple water needs to receive a certain amount of heat fluxto be brought to boil. Once the flow of vapor that has to be compressedand the compression ratio, and therefore the compressor size, areselected, the condenser surface is determined as a function of thetarget heat flux, considering that its surface should be large enough toallow condensation, and reduced enough to be economically reasonable.

The system needs to be highly impervious to prevent contamination of thecondenser 10, i.e. to prevent ingress of non-condensable gases withinthe condenser 10, in order to ensure generation of an air-freepressurized vapor by the compressor. A small amount of steam can bevoluntarily and continuously released after the condenser to make surethat non condensable gases are continuously evacuated from the condenserupstream of the compressor.

As mentioned hereinabove, the evaporating pan 3 operates at a moderatepressure of typically a few water centimeters above atmosphericpressure.

Maple water to be treated (A) is introduced into the evaporating pan 3,through a maple water regulation valve 1 and a heat exchanger 2 fed withcondensate and vapor from the condenser 10 through the pressureregulating valve 11, as heated maple water (B). The maple waterregulation valve 1 may be positioned before or after the heat exchanger2. In the evaporating pan 3, the heated maple water (B) is brought toboiling maple water (C), and generates water vapor (D), which isdirected to the compressor 8 to generate compressed water vapor (F)used, in the condenser 10, to bring the heated maple water (B) toboiling maple water (C), as described hereinabove.

A water/vapor separator 12 may be provided at the output of theevaporating pan 3 to separate water from vapor before entry into theheat exchanger 2, so that the heat exchanger receives only water and theamount of water entering the condenser is reduced as much as possible.

Condensed water (J) may be recovered at an output of the heat exchanger2, through a drainage valve 12. This cold distilled water may be laterreused for cleaning the system for example.

The resulting maple syrup (K) may be recovered in a syrup tank 14 fedfrom the evaporating pan 3 through a syrup valve 13 for example. At themaple syrup exit (K), at a distance from the condenser 10, typically themaple product in the evaporating is below its ebullition temperature. Inorder to ensure a balanced syrup outflow through the syrup valve 13, aheating unit may be added at the output (K), so that the temperature ofthe syrup is higher at the level of the syrup valve 13, and so that thesyrup valve 13 opens adequately. Such regulation mechanism may bedesired when starting the system for example.

The compressor is powered by a motor, such as an electrical or aninternal combustion engine for example. Different types of gascompressors may be used, such as a screw compressor, a scrollcompressor, an ejector, blower etc. . . .

The evaporating pan 3 is shown in FIGS. 3 and 4 with a removableimpervious cover 4.

As shown in FIG. 5, the removable condenser 10 is positioned inside theevaporating pan 3, typically at the bottom.

FIG. 5 shows the condenser 10, with tubing 10 b and manifold 10 a.

As the maple water penetrates in the evaporating pan 3, it has a sugarcontent in an initial range between about 2 and 15 Brix. Aninhomogeneous Brix distribution may be desired within the evaporatingpan 3, from its input to its outlet, as the syrup concentratesprogressively, typically from a sugar content in an initial rangebetween about 2 and 15 Brix to a sugar content of up to 66 Brix.Separating baffles 100, such as stainless steel plates, may bepositioned, perpendicularly to the tubings 10 b of the condenser 10, toallow stratification of the Brix concentration within the evaporatingpan 3, as shown in FIGS. 4 and 5. Such stratification allows a stableregulation of the output valve 13, which is activated in part by theBrix of the outgoing syrup.

Moreover, the bottom of the evaporating pan 3 may be slightly inclined(about ¼ inch to ⅜ inch over the length of the evaporating pan 3 forexample) from the inlet of maple water to the outlet of syrup, so thatthe syrup, denser than the maple water, flows towards the outlet.Inversely, the tubings 10 b of the condenser may be slightly inclinedtowards the opposite direction, so as to assist the condensate waterinto flowing towards the drainage valve 12 mentioned hereinabove.

An aerator may be provided after the heat exchanger 2 before entry intothe evaporating pan 3 to withdraw part of the air contained within theincoming maple water.

In the present system and method, the pressure in the evaporating pan iscontrolled and maintained around atmospheric pressure, therebyeliminating risks associated with maintaining hot water, typically above100° C. under pressure as used in typical systems. The condensercontains only a small amount of water (condensed water (G) in FIG. 2)produced in the condenser 10 at any given time, since the condensedwater may be immediately eliminated through a valve separating liquidfrom vapor.

Thus, the present system does not have to sustain high pressure. Thepresent system retrieves vapor, compresses it, and condensates it, in aservo-controlled way so as to maintain a stable pressure. The pressureunder the cover 4 of the evaporating pan 3 is maintained slightly aboveatmospheric pressure so as to prevent ingress of air within the system.

The present method and system generally allow using the energy availableas vapor for water maple evaporation, the vapor being generated by thevery process of maple water evaporation.

The present system and method use water as the refrigerant fluid. Thepresent system and method allow reaching high coefficients ofperformances (COPs), i.e. ratio between the energy used in the systemfor preheating and condensation, over the energy input into the system,typically between 15 and 22.

FIG. 6 shows a comparison between the performances of an evaporatoraccording to the present invention and a standard oil evaporator asknown in the art, based on the amount of energy required (kWh) toproduce an imperial gallon of maple syrup as a function of the amount ofsugar in the maple water entering the evaporator (Brix), considering acalorific value of oil of 155 890 BTU/imperial gallon, an overallefficiency of the oil evaporator of 74%, 13,25 lb/gallon of syrup, and3412,9 BTU/kWh.

The COP of the system is slightly dependent on the Brix of the maplewater entering the evaporator, since the efficiency of the condenservaries with the viscosity of the liquid. For example, with a maple waterentering the evaporator having a Brix of 2, the COP may be 19, whilewith a maple water entering the evaporator having a Brix of 8, the COPmay be lower, for example 15. With oil evaporators of the prior art, asshown the graph of FIG. 6B, the energy used per volume of syrup is muchmore dependent on the Brix of the maple water entering the evaporatorthan with a system of the present invention. For an initial Brix ofabout 8, the present system reaches a COP of about 14-15, in contrast toa COP of about 0.7 for oil evaporators (about 70% efficiency). For aninitial Brix of about 2, the present system reaches a COP of up to 20.By increasing the surface of the condenser, COPs of up to 22 mayachieved. Even with higher Brix values of maple water entering theevaporator, the present system allows COPs at least 21 times higher thanstandard evaporators using oil, wood, granules or other combustibles.

FIG. 7 shows a table presenting simulated cost gains for a sugar bushcomprising 10 000 notches each producing 2,4 lb of maple syrup, based ona calorific value of oil of 155 890 BTU/imperial gallon, an overallefficiency of the oil evaporator of 74%, a price of 1,25 CAD/I for oil,a price of 0,10 CAD/kWh for electricity, and assuming 13,25 lb/gallon ofsyrup.

As summarized in FIG. 8, the vapor above the evaporating pan issaturated and at a pressure close to atmospheric pressure, i.e. at atemperature of 100° C., the slight overpressure produced by the cover onthe evaporating pan ensuring purity, i.e. low air content, of the vapor,for an efficient heat transfer by the condenser and an optimizedperformance of the compressor. This vapor is pressurized to about 1,4atm, i.e. to a temperature of about 108° C. When forced through thetubings of the condenser, which are immersed in the maple water in theevaporating pan, this pressurized vapor gets oversaturated since thetemperature of the tubings is a little bit lower. The vapor thencondensates on the walls of the tubings, thereby transferringcondensation energy to the water in the evaporating pan, which thusboils and generates vapor, which is recuperated by the condenser. Theenergy of the vapor which escapes from the evaporating pan (condensationenthalpy) compensates for the energy needed for evaporation. it isestimated that the losses of energy are as follows: for 1000 units (1000U) of energy recuperated from the vapor, there may be about 5 U loss tothe motor, about 3 U lost by thermal conduction through the walls of theevaporating pan, 27 U lost through the condensation water (condensate)that leaves the system at a temperature above the temperature of theincoming maple water (for example the incoming maple water is at 2° C.and the condensate is at 12° C.) and 32 U are lost in the hot syrup,which energy is not recovered, the syrup being filtered and bottled whenhot. Those energy losses (67 U) are compensated an energy E_(electric,)input, to the motor for example.

As people in the art will appreciate, the present method and system maybe used in combination with reverse osmosis. Reverse osmosis may be usedto preconcentrate the maple water, i.e. to reduce the amount of watertherein, to reach a sugar content comprised between about 6 and 18 Brixfor the maple water entering the evaporator (A).

As the present system and method allow controlling overheating,caramelization of the maple syrup is prevented and the produced maplesyrup has an optimized content of syringaldehyde, origin of thecharacteristic maple savor.

Although the present invention has been described hereinabove by way ofembodiments thereof, it may be modified, without departing from thenature and teachings of the subject invention as described herein.

What is claimed is:
 1. A system for producing maple syrup or birch syrupfrom maple or birch water, comprising: an evaporating pan undercontrolled pressure; a condenser immersed in maple or birch water insaid evaporating pan; and a compressor, pressurizing vapor generated byevaporation of maple or birch water in said evaporating pan; whereinsaid condenser directs the pressurized vapor provided by said compressorto the maple or birch water within the evaporating pan, thereby furtherevaporating the maple or birch water and further generating vapor. 2.The system of claim 1, comprising an auxiliary heating unit, saidauxiliary heating unit first bringing the maple or birch water to itsboiling temperature so as to first generate vapor needed to start thecompressor.
 3. The system of claim 1, comprising a water nozzle beforean inlet to said compressor.
 4. The system of claim 1, comprisingtemperature controllers, said temperature controllers monitoring atemperature difference between the maple or birch water within theevaporating pan and walls of the condenser.
 5. The system of claim 1,comprising a flow controller, said flow controller monitoring the flowof maple or birch water within the evaporating pan.
 6. The system ofclaim 1, wherein the surface of the condenser is selected according to atarget heat flux.
 7. The system of claim 1, comprising non condensablegases evacuation upstream of the compressor.
 8. The system of claim 1,wherein said evaporating pan operates at a pressure of a few watercentimeters above atmospheric pressure.
 9. The system of claim 1,wherein said evaporating pan operates at a pressure comprises in a rangebetween about 1 and 15 cm of water above atmospheric pressure.
 10. Thesystem of claim 1, comprising a heat exchanger, said heat exchangerreceiving condensate and vapor from the condenser, maple or birch watergoing through said heat exchanger before being introduced into saidevaporating pan as heated maple or birch water.
 11. The system of claim10, comprising a water/vapor separator at the output of the evaporatingpan to separate water from vapor before entry into said heat exchanger.12. The system of claim 10, comprising an aerator after the heatexchanger upstream of the evaporating pan.
 13. The system of claim 1,wherein said condenser comprises at least one generally horizontaltubing immerged under the maple or birch syrup within the evaporatingpan.
 14. The system of claim 1, wherein said condenser comprises atleast one tubing immerged under the maple or birch syrup within theevaporating pan, said tubing being in an inclined position from anoutlet of syrup to an inlet of maple or birch water of the evaporatingpan.
 15. The system of claim 1, wherein a bottom surface of saidevaporating pan is inclined from an inlet of maple or birch water to anoutlet of syrup.